1. Field
Embodiments of the present disclosure generally relate to creating planar surfaces on substrates and on layers formed on substrates, and specifically to chemical-mechanical polishing (CMP).
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a wafer substrate, such as a semiconductor substrate or a glass substrate. As layers of materials are sequentially deposited on and removed from the substrate, the uppermost surface of the substrate may become non-planar and require planarization before further lithographic patterning can be patterned thereon. Planarizing a surface, or “polishing” a surface, is a process where material is removed from substrate surface to form a generally even, planar substrate surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess material which has been deposited to fill the features, and to provide an even surface for subsequent lithography-based patterning steps.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique for planarizing substrates. CMP utilizes a fluid chemical composition, typically mixed with an abrasive to form a slurry, for selective removal of material from the surface of a substrate. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly to position a substrate secured therein in contact with a polishing pad in a CMP apparatus. The substrate carrier provides a controllable pressure to the substrate urging the substrate against the polishing pad. The polishing pad is moved relative to the substrate by an external driving force. Thus, the CMP apparatus creates polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a fluid polishing composition, or slurry, to effect both chemical activity and mechanical activity. The polishing pad has a precise shape to distribute the fluid and contact the substrate. The polishing pad may be cleaned to remove debris which would otherwise collect upon the polishing pad and cause damage to substrates processed therewith and reduce the polishing pad life.
In some cases, fluid may comprise ten-nanometer sized abrasive particles comprised of metal oxides, for example, silica (SiO2), alumina (Al2O3), cerium oxide (CeO2), and titanium oxide (TiO2) suspended in an aqueous solution, such as potassium hydroxide (KOH). Other fluid compositions are possible. As part of the polishing process, debris generated from the working surface of the substrate enters the fluid and also collects on the polishing pad. This debris can cause various issues that can in some issues be problematic, such as creating scratches on the substrate surface and contamination of later-polished substrates. Thus, the contaminated fluid and the debris collected on the polishing pad need to be dislodged from and removed from the polishing pad. Dislodgement and removal of debris and/or contaminated fluid may occur before, during, and/or after polishing depending upon the requirements of the substrate being polished. Current methods of removal have included water rinsing and vacuum using high-energy liquid or gas flows to disengage the fluid and/or debris from the polishing pad. Once disengaged, the challenge becomes to remove the fluid and/or debris without backwash and/or spray-back to the polishing pad which can be issues with current approaches. What are needed are new approaches to disengage and remove fluid and/or debris from the polishing pad without backwash or spray-back to the polishing pad.